The present invention is directed to auxiliary systems for internal combustion engines, and in particular to emissions control systems, for motor vehicles.
It has become known that the level of pollutant hydrocarbons, which every hydrocarbon fuel based internal combustion engine produces as a product of combustion, can be reduced, during periods of deceleration or idling, through the injection of oxygen-rich air, which is at ambient temperature, or at least at a temperature substantially below that of the gases in the exhaust manifold. Prior art systems to accomplish this air injection typically employ an air pump and a system of pipes which draws oxygen-rich air from a "cool" air source, such as the ambient air, and channels the oxygen-rich air directly to multiple locations immediately adjacent to the beginning portions of the exhaust manifold, near each cylinder port to promote the combustion of the non- or partially combusted fuel which the exhaust gases contain. The operation of the air pump may be controlled by a solid-state computerized control, as is typically found on current motor vehicles.
Current motor vehicles also employ an exhaust gas recirculation (EGR) system, to redirect a portion of the exhaust gases from the exhaust manifold back into the intake side of the engine, so as to mix with the air going into the engine to lower the combustion temperature and dilute the fuel/air mixture to reduce certain pollutants and to improve fuel economy at cruising speeds. Such recirculation of the exhaust gases is effective and desired particularly during periods of acceleration and steady-state throttle at cruising speeds. A typical exhaust gas recirculation system uses a separate system of high-temperature resistant piping to channel some of the hot gases from the exhaust manifold through an electro-mechanical valve back to the throttle body or the intake manifold. The intake manifold end of the EGR system can employ some form of heat transfer isolation, as the materials of the intake manifold can often be configured from non-high-temperature resistant materials, so as to prevent transfer of heat from the gases directly to the structure of the intake system, prior to mixing of the exhaust gases with the intake air or air/fuel mixture.
The use of separate piping systems for both the air injection system, and the EGR system has the drawback of additional weight, and additional cost of assembly labor and components. For example, each connection of an air pipe to each exhaust manifold port usually employs a threaded fitting, a relatively costly component. Also, each manifold port requires costly machining to receive each air pipe. It is therefore an object of the invention to provide a lower cost integrated air injection/EGR system which can make use of a common piping arrangement, which is capable of directing "cool" oxygen-rich air into the exhaust system, during deceleration or idling periods of operation, and of directing hot exhaust gases into the intake system, during acceleration and cruising periods. The two systems are incapable of operating simultaneously.
It is a further object of the invention to provide such an integrated air injection/EGR system as described, but which protects those portions of the air injection system, such as the air pump, which are sensitive to high temperatures, from the potentially damaging effects of the high-temperature exhaust gases.
Still another object of the invention is to provide such an integrated air injection/EGR system such as described, which additionally protects against the misdirection of the air and exhaust gases through the integrated system.
These and other objects of the invention will become apparent in light of the present Specification, claims and Drawings.